Clamps for establishing such connection are known in the art and are conventionally attached to one end of the power cord of the power consuming units to be connected to the power source.
They comprise at least one ring-shaped portion made of an electrically conductive material whose circumference is open at one section thereof. The ring-shaped portion is adapted to be axially fitted to the male terminal, with a predetermined radial clearance, and clamped thereto until it creates a proper and stable electrical contact between the outer surface of the terminal and the inner surface of the ring. Clamping is obtained by screw mechanisms. The latter act on two opposed and spaced-apart jaws, which radially project out of the circumference of the ring-shaped portion of the clamp and are placed at the ends of the open circumference section, draw them toward each other and hence clamp the ring-shaped portion around the body of the male terminal by eliminating the radial clearance. This will prevent accidental axial removal of the clamp and provide proper constant power supply to the power consuming units.
Conventionally, the ring-shaped portion of the clamp is manually clamped by an operator, who acts on the screw mechanism when said ring-shaped portion is entirely axially fitted on the male terminal, parallel to the base of the source from which the frustoconical body of the terminal projects.
In order to prevent the ring-shaped portion of the clamp from being clamped when said ring-shaped portion has not yet reached the proper axial position on the frustoconical body of the male terminal, i.e. when the ring-shaped portion is not yet proximate and parallel to the base surface from which the frustoconical body stands up, the clamps are known to be equipped with safety devices that allow proper identification of the position in which clamping has to be made.
This will prevent shocks or vibrations of the source from loosening the clamp and breaking the connection to the power consuming units.
A known type of safety device, as disclosed in Patent Application Publication EP 3 264 534, comprises a plate-like element, which is also made of an electrically conductive material, and has a circular opening with a diameter greater than the greatest diameter of the frustoconical body of the male terminal, connected to the ring-shaped portion of the clamp. According to the embodiment as described in the aforementioned patent application, the plate-like element is hinged to the outer edge of the ring-shaped portion of the clamp in a position opposite to the position in which the clamping jaws are located, on the side from which the clamp is to be fitted onto the male terminal. Said plate-like element is held in an angularly displaced position relative to the plane of the opening of the ring-shaped portion, by elastic means operating between such ring-shaped portion and the plate-like element.
When the clamp is axially fitted onto the frustoconical body of the male terminal, said plate-like element is the first to reach a position proximate and parallel to the base surface from which the male terminal stands up and keeps the ring-shaped portion lifted and tilted relative to the axis of the frustoconical body of terminal, thereby indicating that the position of the ring-shaped portion is not a correct clamping position.
According to the aforementioned prior art, the plate-like element is equipped with screw members for clamping the ring-shaped portion of the clamp but these members only exert their clamping action on the jaws of the ring-shaped portion of the clamp by overcoming the action of the interposed elastic means, after angularly displacing the ring-shaped portion relative to the plate-like element to a position parallel thereto. Then, since the ring-shaped portion is also adjacent and parallel to the base surface of the source from which the male terminal stands up, the position is deemed to be the correct clamping position for the clamp.
A different known technology to determine the correct position of a clamp before clamping it on a male terminal, is disclosed in U.S. Pat. No. 5,302,143.